Process for the electrostatic separation of clay containing crude potassium salts

ABSTRACT

Crude argillaceous potassium salts are separated by first subjecting the crude salt to a conditioning with 2,6dinitrophenol or a mixture of said dinitrophenol, a halogenocarboxylic acid and water and thereafter the thusconditioned salt is passed through an electrostatic separator in which a warm atmosphere is maintained, thereby producing a separation of the particles of the salt into two fractions, one containing clay and rock salt at the positive electrode and the other containing sylvite and kieserite at the negative electrode of the electrostatic separator.

Singewald et al.

[ 1 Sept. 17,1974

PROCESS FOR THE ELECTROSTATIC SEPARATION OF CLAY CONTAINING CRUDEPOTASSIUM SALTS Inventors: Arno Singewald, Kassel; Gunter Fricke,Neuhof; Detlef Jung, Meitingen, all of Germany Assignee: Kali and SalzAG, Kassel, Germany Filed: Aug. 22, 1972 Appl. No.: 282,839

US. Cl 209/9, 209/11, 209/127 R Int. Cl. B03b l/04 Field of Search....209/9, 127 R, 127 A, 127 B,

References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS722,888 6/1942 Germany 209/127 R 1,078,961 4/1960 Germany 209/127 R2,007,677 9/1971 Germany 209/9 Primary ExaminerRobert Halper Attorney,Agent, or Firm-Michael S. Striker [57] ABSTRACT Crude argillaceouspotassium salts are separated by first subjecting the crude salt to aconditioning with 2,6-dinitrophenol or a mixture of said dinitrophenol,a halogenocarboxylic acid and water and thereafter the thus-conditionedsalt is passed through an electrostatic separator in which a warmatmosphere is maintained, thereby producing a separation of theparticles of the salt into two fractions, one containing clay and rocksalt at the positive electrode and the other containing sylvite andkieserite at the negative electrode of the electrostatic separator.

9 Claims, No Drawings PROCESS FOR THE ELECTROSTATIC SEPARATION OF CLAYCONTAINING CRUDE POTASSIUM SALTS to which the salt is exposed is between2 and 20 and most preferably between 5 and 15 percent. The salt isheated prior to the charge. The amount of 2,6- dinitrophenol should bebetween 50 and 500 g/t, prefhalogenocarboxylic acid and water andthereafter the 5 erably between 75 and g/te a ogenothus-conditioned saltis passed through an electrostatic carboxyhc acid Preferably ischloroacetic acid which separator in which a warm atmosphere ismaintained, may be used in amounts of 50 to 500 h Ph y 0f therebyproducing a separation of the particles of the 75 to 300 The watershould be pfesem m amounts salt into two fractions, one containing clayand rock between 1 and 4'0O0 preferably m an amount salt at the positiveelectrode and the other containing 10 tween and 99 f' sylvite andkieserite at the negative electrode of the The of condmonmg by mtens've"F' may be electmstatic separaton between and 120 sec. and preferably lSbetween 20 and 60 sec. The separation is preferably effected at aBACKGROUND OF THE INVENTION temperature between about 25 and 65 C.

In German Pat. No. 2,007,677 an electrostatic sepah following exampleswill further illustrate the ration process is described for argillaceouscrude potasventlon' I I sium salts wherein the salt is treated withlactic acid in The stfmmg P m examples was a y combination with ahalogenmcarboxyhc acid and mite having the following chemical and screenanalysis: wherein the thus conditioned mass after heating to atemperature between and 65 C is then separated 20 h i Analysis in anelectrostatic separation. At the positive electrode clay separates outwhile the virtually clay-free crude KC| 18.61% salt is deposited at thenegative electrode. The crude 1 4 salt from which the clay thus has beenremoved can M553 2323; then be further processed to obtain highpercentage CaSO, 0.63 sylvite concentrates. :38

SUMMARY OF THE lNVENTlON 51 m It has now been found that when theconditioning is effected with dinitrophenol, specifically 2, 6- MineralAnalysis dimtrophenol, or a mixture of such dinltrophenol, ahalogeno-carboxylic acid and water a reversal of the s me 7 polarity ofthe charge is effected in the salt. As a result Lingbeinite theargillaceous minerals will be charged negatively to- 9 y l f M getherwith the rock salt and both can therefore be ob- ,i'fifi'fifi 31 3:tained directly as residual fraction. Such reversal does c sa t 5 .0 notoccur with the sylvite and kieserite. These two ma- Clay terials aretherefore deposited together at the positive electrode. There is thusobtained a sylvite-kieserite fraction which can either be used directlyas a valuable 40 Screen Analysis K-Mg-fertilizer or can be furtherprocessed to obtain a high percentage sylvite or kieserite concentrate.There 0 8 8g is thus obtained a selective charging of the argillaceousmm materials and of the rock salt on one hand and of the 0.25 0.16 mm8.0 7. sylvite and kieserite on the other hand. 8'}

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, ln the Tables below the following symbolshave been both as to its construction and its method of operation, d;together with additional objects and advantages f ti at the positiveelectrode thereof, will be best understood from the following de- Mmiddlings. scription of specific embodiments when read in confraction atthe negative electrode. nection with the accompanying drawing. EXAMPLE 1DETAILS OF EE L S E GESF SPECIFIC The tests incorporated in this Examplewere carried I out at a 10 percent relative humidity corresponding toPreferably the conditioning is effected by vigorous an b lute airhumidity at 3947C of 57 g/m The mixing of the conditioning agent oragents with the separations were effected in a gravity (free nurse 5amernd p iu m salt lireferablythe relative humidity tor with a throughputof about 10 t/m h:

TABLE 1 Test Conditioning K,0 contents NaCl contents Clay contents 7cNo. Agent g/t 1 Fatty acid 32.2 2.2 45.4 l8.l 3.4 0.9 2 qrtbp s tis i 02 6. ,5 1 7 54-8. 0,7,.

2,6-dinitrophenol The tests Nos. 1 and 2 as well as Nos. 3 and 4illustrate the prior art. They show that the argillaceous minerals havethe same charge as the sylvite (Tests Nos. 1 and 2 or that they have thesame charge as the rock salt and kieserite while the opposite charge isplaced on the sylvite (Tests Nos. 3 and 4 which illustrate the processof the above-mentioned German patent).

Test No. 5 illustrates the process of the present invention. As appearsby using 2,6-dinitrophenol as conditioning agent an equal negativecharge is placed on the clay and rock salt as against the sylvite andkieserite. Accordingly there are obtained virtually clay-freesylvite-kieserite fractions at the negative electrode which can then befurther processed to obtain sylvite and kieserite concentrates. TheNaCl-fraction which is high in clay and comprises 78.0 percent NaCl and4.1 percent HCl insoluble material accordingly contains only about 6 to10 percent of the total initial sylvite. This fraction can then bedischarged directly as the residual fraction and can thus be eliminatedfrom the subsequent sylvite processing operation.

EXAMPLE 2 This Example illustrates that chloroacetic acid and waterimprove the effects obtained by the dinitrophenol. The sylvite then iseliminated to a higher degree in the concentrate and rock salt iseliminated at a higher amount in the residue. The combination ofconditioning agents comprising 2,6-dinitrophenol, chloroacetic acid andwater constitutes the optimum of the simultaneous separation of rocksalt and clay on one hand and sylvite and kieserite on the other hand.

The following Table further illustrates a test with the combination of2,6-dinitrophenol, H 0, and trichloroacetic acid. ln this test therewere used the following amounts: 200 g/l dinitrophenol, 1,500 g/! waterand 300 g/! trichloroacetic acid. The separations were carried out at arelative humidity of 5 percent corresponding to 55C at an absolutehumidity of 5.5 g/m.

TABLE 11 NaCl Kieserite l-lCl (insoluble) Contents (71) Crude saltConcentrate Residue racttons (7r) Crude salt 1 Concentrate Residue(residue") eliminated at the positive electrode.

The process of the invention permits to obtain a common charge betweenthe clay and the rock salt as against the charge on the sylvite andkieserite. From a crude salt containing 12.2 percent K 0 and 2.5 percentHCl insolubles there were obtained, at a single pass through theseparator, a concentrate with 26.6 percent K 0 and only 0.4 percent HClinsolubles at the negative electrode. The sylvite recovery in theconcentrate was 93.5 percent.

The clay fraction in the residue contained 93.7 percent of the claywhich had been introduced with the crude salt and was thus eliminated.At the same time 84.5 percent of the rock salt were also eliminated inthe residue.

These figures illustrate the substantial advance of the process of theinvention. The separation operation can be carried out with throughputsof 5 to 30 t of crude salt per meter of width of electrode and hour.This means that the size of the electrode (width) can be reduced 30 totimes as against the prior art. This thus permits huge savings inapparatus investment and cost of operation and also results in asubstantial increase of the safety of the operation.

The high selectivity regarding the clay of the process of the inventionis such that the clay is practically quantitatively eliminated from thesalt in a single stage operation. There is thus obtained at the negativeelectrode a virtually clay-free crude salt which is high in K 0 contentsand which can then be further processed in well known manner to obtain ahigher K 0 yield and maximum concentrates with at least 60 percent. Thiscrude salt which is free of clay and high K 0 contents has been freed ofmost of the rock salts. Thus in a subsequent sylvite separationoperation only a comparatively low amount of salt will be deposited.This again leads to substantial savings in investments and cost ofoperation.

As has already been indicated the inventors have also found that watersubstantially increases the effects of the 2,6-dinitrophenol. The amountof water to be used dependson the relative humidity of the atmosphere towhich the salt has been exposed prior to the treatment with theconditioning agents and prior to the heating to the separationtemperature. Thus at a high relative humidity of the atmosphere lesswater need be added during the condition while the amount of water ishigher at a low relative humidity. The amount of water that must be usedvaries between 1 and 4,000 g/t, and preferably is between 500 and 3,000g/t.

EXAMPLE 3 The tests of this Example further illustrate the substantialadvance of the process of the invention. 1. Clay and NaCl. separationaccording to the process of the invention are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimedas new and desired to be protected 5 6 TABLE [II byLetters Patent is set forth in the appended claims: 1. In a process forthe electrostatic separation of par- Hcr Hci ticles of a crudeargillaceous potassium salt which in- K20 NflCl em K2 p cludes clay,rock salt. sylvite and kieserite in which the 3% il fi {a as 5 particlesof the crude salt are first subjected to treat- (7I) ment with aconditioning agent and are then charged Crude salt 2.2 520 2'5 100 100electrostatically and passed through an electrostatic Concentrate 28.021.0 0.5 92.7 9.4 separator to separate the components of the crude ar-Residue gillaceous potassium salt into two fractions containing 10different proportions of its individual components. the ll. Separationof the concentrate by conventional flotaimprovement which comprisesconditioning the partition process: W clesof the crude salt intimatelymixing them with a TABLE IV K o-yield K O-contents relative to relativeTest 7c initial flotato crude No. concentrate residue tion mass salt lwithout electrostatlc pretreatment 40.0 2. l 2 86.l 86.] 2 afterelectrostatic pretreatment according to invention 48.6 1.38 97.8 90.6

The clay and NaCl separation according to the proconditioning agentconsisting of 2-6-dinitrophenol or a cess of the invention was carriedout by conditioning of mixture of 2,6-dinitrophenol and ahalogenocarboxylic the argillaceous crude salt with 200 g/t 2,6- acid ofthe group consisting of monochloroacetic and dinitrophenol, 1,000 g/twater and 300 g/t trichloratrichloroacetic acids and water, passing thethuscetic acid at a relative humidity of 7.5 percent in 30 conditionedparticles through an electrostatic separa heated air. tor in which awarm atmosphere having a relative hu- The subsequent separation byflotation of the virtumidity between 2 and percent is maintained,thereby ally clay-free concentrate of high K 0 contents was efseparatingat the positive electrode a fraction predomifected with g/l guar flour,50 g/t amine, l5 g/t oil nantly comprising clay and rock salt and, atthe negaand l5 g/t of a water insoluble flotation foamer consistliveelectrode, a fraction predominantly comprising syling of intermediateand higher ether-alcohols (sold vite and kieserite. under the trade-markFlotanol by the Farbwerke Ho- 2. The process of claim 1 wherein the saiddinitro- U- This is represented y test 2 O Table phenol is employed inamounts between 50 and 500 g/t. Test No. l of the same table has beenadded only for 3. The process of claim 1 wherein the dinitrophenolcomparison purposes to show the direction flotation of i mployed inamounts between 75 and 200 g/t. a crude salt without electrostaticpreceding prepara- 4. The process of claim 1 wherein the conditioning istion. effected by vigorous mixing for a time betwee l0 and The directflotation of the argillaceous crude salt re- 120 ds, sulted in aconcentrate o 0- PerCeht 2 Which was 5. The process of claim 1 whereinthe conditioning is equivalent to a K 0 yield of 86.1 percent. Theflotation ff t d by vi mixi for a time betw e 20 and after treatment ofa substantially clay-free concentrate 60 d as obtained by the process ofthe invention which was 6, Th ess of laim 1 wh in the electr t ti highin K 0 contents is shown in test No. 2. In this case separation i i d tt a tem t b tween there was obtained a flotation concentrate of 48.6perabout 25 d 65 C Cent 2 Relative to the mass p y for the flota- 7. Aprocess as defined in claim 1 in which the relaon step which wasconstituted by the concentrate Obtive humidity is maintained between 5and 15 percent tained in T 1 the 2 Yield was 973 Pereehh 8. A process asdefined in claim 1 in which the condi- Relative to the crude Sal t 2 yiwas P tioning agent consists ofa mixture of 2,6-dinitrophenol, cent. thehalogenocarboxylic acid and water, in which mix- The Preliminary ySeparation y the ProceSS of the ture the amounts of 2,6-dinitrophenoland halogenoinvention therefore results in better K 0 concentrates b liid are h between 50 d 500 grams per and better 2 Yields in theSubsequeht y TeeOV' metric ton of the crude salt and the amount of wateris ery process. between 1 and 4,000 grams per metric ton of the crudeWithout further analysis, the foregoing will so fully le reveal the gistof the present invention that others can 9, A process as defin d inclaim 8 in which the cohdi. by applying current knowledge readily adaptit for Varitioning agent consists ofa mixture of 2,6-dinitrophenol,applications without omitting features that, from the halogenocarboxylicacid and water, in which mixthe stahdpoiht of Prior fairly constituteessential ture the amount of2,6-dinitrophenol is between 75 andcharacteristics of the generic or specific aspects of this 200 grams permetric ton, the amount of the halogenoinvention and, therefore, suchadaptations should and carboxylic acid is between and 300 grams permetric ton, and the amount of water is between 500 and 3,000

grams per metric ton of the crude salt.

2. The process of claim 1 wherein the said dinitrophenol is employed inamounts between 50 and 500 g/t.
 3. The process of claim 1 wherein thedinitrophenol is employed in amounts between 75 and 200 g/t.
 4. Theprocess of claim 1 wherein the conditioning is effected by vigorousmixing for a time betwee 10 and 120 seconds.
 5. The process of claim 1wherein the conditioning is effected by vigorous mixing for a timebetween 20 and 60 seconds.
 6. The process of claim 1 wherein theelectrostatic separation is carried out at a temperature between about25* and 65* C.
 7. A process as defined in claim 1 in which the relativehumidity is maintained between 5 and 15 percent.
 8. A process as definedin claim 1 in which the conditioning agent consists of a mixture of2,6-dinitrophenol, the halogenocarboxylic acid and water, in whichmixture the amounts of 2,6-dinitrophenol and halogenocarboxylic acid areeach between 50 and 500 grams per metric ton of the crude salt and theamount of water is between 1 and 4,000 grams per metric ton of the crudesalt.
 9. A process as defined in claim 8 in which the conditioning agentconsists of a mixture of 2,6-dinitrophenol, the halogenocarboxylic acidand water, in which mixture the amount of 2,6-dinitrophenol is between75 and 200 grams per metric ton, the amount of the halogenocarboxylicacid is between 75 and 300 grams per metric ton, and the amount of wateris between 500 and 3,000 grams per metric ton of the crude salt.